Georg Simon Ohm (1789-1854), a German physicist and mathematician, was intrigued by Volta’s voltaic pile. He found there is a direct proportional relationship between the potential difference (voltage) applied across a conductor and the resultant electric current. This relationship is known as Ohm’s Law: voltage is the result of amperes x resistance. It is written as V= IR, where V is voltage, and R is resistance. “I” is used for amperage because it stands for “intensité du courant” (current intensity), as used by Ampère.
As a unit of resistance, the ohm was defined as expressing the resistance in a circuit transmitting a current of one ampere when subjected to a potential difference of one volt.
Electricity is sometimes compared to water flowing through a pipe. In that example, the rate of flow can be compared to the amperage, the pressure of the water can be compared to voltage and the diameter of the pipe can be compared to the resistance.
Fun facts: Ohm also worked on the principles of acoustics and wrote a textbook on geometry